The Mutant and Me
by mosylu
Summary: Of all the things to be cursed with, a little brother is the worst. And maybe the best. Family AU, absolutely positively NOT Snowbarry.
(A/N) To me, Caitlin was always the big sister (fussy, mom-ish, and in a state of continual exasperation) to Barry's little brother (mischievous, teasing, and certain that she can and will fix every screw-up). So I decided to explore that dynamic with an actual family AU.

* * *

 **5th and 3rd grade**

Barry hung over the back of the couch. "Whatcha reeeeadin'?"

"A magazine," Caitlin said. "Go away."

"Is it about how to do your haaaaaaaair?"

"It's about DNA."

"Whuh?"

"DNA is, like, the computer code of your body. It tells everything how to grow." She tipped her head back to sneer at him. "DNA is the reason you're a shrimpy little twig boy."

He stuck his tongue out. "Am not. Dad says I'm gonna grow anyways. Why do you care about deena?"

"D.N.A," she said, biting off each letter. "Because if you could rewrite DNA, you could change things about your body."

His eyes gleamed. "So, could you make a _mutant?_ "

"You're a mutant," she snapped. "Leave me alone."

He scowled and grabbed for the magazine, yanking it out of her hands before she could react. She let out a shriek and leapt off the couch, and he took off running. For such a shrimp he was wickedly fast.

But she was still taller, with longer legs, and she tackled him to the ground on the front lawn, wrestling it out of his hands. It ripped in half.

"You turdnugget! Look what you did!"

He rolled over. "That was you!"

His nose was bleeding and she battled back a surge of guilt. He should have known better than to take any of her stuff.

* * *

When her entire stash of science magazines disappeared, she charged into his room and searched all his hiding places until she found them in a shoebox under his bed.

"Look at this! He drew all over the pages!" she ranted to her mother.

"It looks like he was marking things that he wanted to look up," her mom said. "I know I helped him find something at the library about this."

Caitlin didn't care. "These are mine!" she screamed. "Why did he pick now to get all interested in science?"

"Honey, he's interested because you're interested. He idolizes you, he always has!"

"I don't care why he wants to copy me all the time. Can't he be into cars or sports or video games? Can't I have _one thing_ that's mine?"

"That's enough, young lady!"

"But - "

"Sit!"

Caitlin sat.

Her mother glared down at her. "You're welcome to be interested in anything you want. So is your brother. Science is not off-limits to Barry because that's your focus right now. He may forget about it next week. You may forget about it next month."

Her eyes narrowed. She was not going to lose interest in science and start reading fashion magazines or something.

"But while either or both of you are interested, then your interest will be encouraged equally. I'm not saying you have to share your magazines. What I am saying is that the world is big enough for both of you, and you are going to be siblings your whole life, and you could do worse than to share an interest. And you're not allowed to tell your brother what he is and is not permitted to find fascinating."

Caitlin scowled at her knees.

"Do you hear me, young lady?"

"Yes, mom."

* * *

 **7th and 5th grade**

In spite of the blue ribbon she clutched, Caitlin frowned.

Barry had gotten second in his grade.

Second!

He'd lost to a kid who'd made a remote-controlled robot. Come on. Any toy company could make a stupid robot. Were those judges blind? Couldn't they see that Barry's project had been far more interesting and original?

Robot.

Pft!

Barry came bounding up. "Caitlin! Second! Look!" He waved his red ribbon in her face.

She glared at it. His face fell. "Nice," he said. "I'm still not allowed to like science? Whatever."

"You should've won," she said angrily.

His face went blank with surprise. "It's - second's good."

"You should've won," she insisted. "Your project was really good, Bare."

"You think so?"

"No, I'm lying," she said. "Of course I think so. Why would I say that if I didn't think so?"

He shuffled his feet. "I dunno … anyway, Cisco's was better."

"Who's Cisco?"

"The robot kid. Did you see this? Come see this!" He grabbed her hand and dragged her through the regional science fair.

The robot kid was a tiny Latino boy that she'd seen and mistaken for a third-grader. His hair hadn't been cut in a little too long and he was swimming in a Star Wars t-shirt, but his smile as he showed off his robot to a group of kids shone like a spotlight.

Barry waved, jumping up and down to be seen. "Cisco! Heyyyy!"

"Barry!" the boy yelled, jumping up and down, possibly out of sheer excitement. The onlookers drifted off.

"Cisco! This is my sister, Caitlin." He grabbed her hand with the blue ribbon in it. "Look! She won first place for seventh grade."

"Oh," Cisco said, dark eyes going wide. "Oh my god. You did the plant thing. The thing with the plants and the colored lights and - Oh my god! That was so rad!"

"Rad?" she said. She'd heard that word in eighties movies. "How old are you?"

"Eleven," he said without shame. "I saw it on an old TV show. I'mma start using it. I predict it'll catch on. Like, retro."

"Rad," Barry said, and they grinned at each other. "Dude! Can I try your robot?"

"Yeahyeahyeah!" Cisco all but shoved the remote control into his hands and they settled down, hunched over the robot.

"Looks like your brother found his new best friend," her dad said from behind her.

"Well, that'll be a switch from not having one at all," she said.

Her father just laughed and hugged her from behind, resting his chin on the top of her head.

"He's a nice kid," Caitlin admitted.

"A very nice kid. No competitive streak at all."

"Was that aimed at me?"

"It's not bad, honey, you just have to make sure that you balance it out with sportsmanship. Like them."

"I did get first," she said.

"You did." He kissed the top of her head. "I'm proud of you. I'm proud of both of you."

* * *

 **10th and 8th grade**

Caitlin's mom knocked, then stuck her head in. "Ronnie's here, honey."

Caitlin bit her lip. "How do I look?"

"Adorable."

"Mommmm," she whined. She didn't want to look adorable, like a bunny rabbit or a puppy. She wanted to look hot and sexy and like somebody that Ronnie Raymond would want to date again.

"Very nice and very appropriate for an almost-sixteen-year-old young lady."

That was not very much better, but what could you do with parents, really? She sighed. "Did you leave him on the porch or something?"

"No, he's downstairs in the kitchen, talking to your brother."

She sucked in her breath. "Mom! That's even worse!"

She rushed down the stairs in time to hear Barry said, "You don't have a condom in here. Is that because you intend to respect my sister, or because you don't think you need to wrap it up? Because I'm here to tell you - "

She charged into the kitchen, ripped Ronnie's wallet out of her brother's hand, and snarled, _"Bartholomew. A word."_

She dragged him into the hallway, trying not to think about how wide Ronnie's eyes had been. "What! Was! _That?!"_

"I was trying to look out for you!" At some point in the last year, he'd achieved enough height that they were eye-to-eye, but his voice still cracked at unexpected times.

"By humiliating me in front of my date?"

"I wanted to make sure he'd treat you right! What if he thinks you're supposed to - to - you know - because he bought you popcorn?"

"Do you seriously think I'd go out on a date with a guy who was like that?"

"You can't tell. And he's a jock! He's got a varsity jacket for football and everything! You know what they're like!"

"Look, just because some soccer players in the eighth grade use you and Cisco as their personal daily punching bags does not mean that all jocks are jerkholes. Besides, Ronnie might be kind of a jock, but he's also kind of a nerd. We've been chem partners for an entire semester and he's really nice and he would never do - what you're saying." She felt her cheeks heat.

"How do you know?"

"Well, I don't, not really - "

"Hah!"

"But if that happens, do you honestly think some kind of threat from a scrawny twerp is going to scare him more than I could?"

He withered. "No." He paused. "He's actually pretty cool. He talked me really nice. Like I was a human being. He didn't even think it was weird that I asked to see his driver's license."

Barry was a little obsessed with drivers' licenses lately. Caitlin's working theory was that he dreamed of driving extremely fast in a red convertible with a certain adorable fellow eighth-grader in the passenger seat.

It was a point in Ronnie's favor, that he'd looked at her spindly, nerdy brother, and treated him kindly enough that Barry wanted to let her know about it. "You see why I agreed to go on a date with him?"

"I guess."

She patted his cheek. "I appreciate that you tried to look out for me. Now listen up, mutant." She poked him in the chest. "Whether or not Ronnie has a condom, and what he intends to do with it or not do with it, and how I intend to react to that, is none of your business."

He started to say something.

"Nuh-uh-uh-uh! Me, not you. Who?"

"You."

"Not who?"

"Me."

"Exactly. If you," she said, "ever again do something so _patronizing,_ so _paternalistic_ , I will break off all your fingers one by one and stick them in every orifice you own. Clear?"

He nodded, wide-eyed.

"Good." She sailed into the kitchen. "I apologize for my mutant brother," she said with tremendous dignity. "He won't be speaking to you again. Or possibly ever."

Ronnie nodded. "No. It was - fine. Really. Kinda sweet."

"It was horrible. He's horrible. Let's go." She took his hand and dragged him out the front door, yelling, "Bye, I'll be back by curfew!" over her shoulder.

* * *

 **11th and 9th grade**

"Hey, mutant," she said.

"Hey," said the lump under the covers.

"Move," she said, and the lump scootched over enough so she could sit. "What happened?"

"Mmmfffmmmooo," the lump said.

She peeled the blanket off his head. "What?"

"She said no."

"I figured that out." Because if Iris West had said yes to going to homecoming with him, Barry would have hired a skywriter. Or possibly gotten his best friend to build something that would do it. That sounded like something Cisco would be all over. "Well, I'm sorry."

"She's already going with somebody."

Caitlin looked at the ceiling, thinking, _Well, if you hadn't waited until two weeks before the dance, dumbass. Why are you surprised?_ "Who?"

"Eddie Thawne," Barry said with clear loathing.

"Who's that?"

"A _sophomore_." Barry said it the way someone else might have said, _A baby-eater._

"A jerk?"

A pause. "No," Barry muttered. "He's okay."

Except that he was going to homecoming with the girl of Barry's dreams. "It's one dance," she said.

"What if they start dating?"

"Then they date. And then, probably, eventually, they break up. It's high school, Bare. She's a freshman. Do you know how many girls are with the boy they dated freshman year? Or even sophomore year?"

"But you and Ronnie haven't broken up yet."

"Yes, well, we're an exception."

"What if they're an exception?"

"Chill. Don't doom yourself to a loveless life just yet. Look, go to the dance anyway. Have warm punch and dance like a weirdo. You'll have fun."

"By myself?"

"Go with Cisco."

"He's got a date."

"Cisco's got a date?"

"A boy from his English class."

"Well, then, find someone else to go with. Your friend Patty? She's cute. Does she have a date?"

"Mmm. I don't think so."

"See? There you go. Or somebody. Or nobody. Just go."

"Hey. Caitlin. What if - "

She swung her legs off the bed. "Don't even think about trying to go with me and Ronnie, mutant." They had big plans for Ronnie's last homecoming dance, and they did not include her little brother hanging around.

* * *

 **12th and 10th grade**

Caitlin burst into the living room. "Did the mail come yet? I saw the mail truck."

"Mmm," Barry said, nose deep in the Scientific American website. "Yeah."

"Annnnnndddd?"

He shrugged. "Nothing interesting."

She wilted. "Ugh! No! Still? Gah." She drooped out of the room, trying not to think about Central City University's early-admission dates.

"Hang on," he called out. "Maybe there was something besides pizza coupons. Maybe something in a big envelope?"

She whirled and saw her brother holding up a big white envelope with the CCU logo plastered over it. She lunged for it, saw the words _Welcome to the freshman class!_ and screamed. "I got in!"

"You got in!" he yelled back.

"I got in, I got in!" They jumped up and down, shrieking at each other until their parents came downstairs to see what all the yelling was about.

* * *

Barry knocked. "Um," he said.

"You can come in."

He slouched in the doorway. "I wanted to, um, say. Ronnie's stupid, and his face is stupid, and if you want me to go beat him up, I will."

"No, I don't want you to beat him up," she said. "This - this kind of thing happens, Bare. I mean, he's six hours away. And he's in college, and I'm still in high school. It's a big difference. We're not the first couple to break up like this. We're not even the first couple this month."

"But you guys were in love."

"Things don't always work out even when you really want them to." She wiped her eyes and managed a smile. "We tried. We put our best effort into making a long-distance relationship work. And he'll always be the first boy I really loved. But it's hard. Next year would have been even harder, with me at CCU. It happens. Breakups happen."

He put his arm around her. She leaned into his shoulder.

"I'm glad you don't want me to beat him up," he said after awhile.

"C'mon, you're six inches taller than he is."

"Yeah, but I swear he outweighs me by thirty pounds."

"All muscle, too." She poked him in the ribs and made him yelp. "Thanks for the offer. It was nice."

"I'd do it. I could drive out to State to beat him up right now. Cuz, you know, I have my driver's license."

She smiled against his shirt. "Really? Do you? Because you haven't mentioned it at all."

* * *

 **College and 12th grade**

When her phone rang and she saw his picture on the screen, she picked it up. "Rescue me," she said dramatically. "Rescue me from Sociology."

"Hey," he said. "Uh. So. You know how I was going to apply to CCU next year?"

"Yeah. You and Cisco are still not sharing my off-campus apartment. Not even, mutant."

"I'm thinking maybe I'm … not? Going to apply there?"

"You're not? Where do you wanna go instead?"

"I was thinking maybe …" his voice dipped. "SCU?"

"You want to stay in Starling?"

"Maybe. Yeah?"

"Is this about Iris? Is that where she's going?"

"They have a great journalism school."

"You're not going to be a journalist! Are you?"

"No. Still chem, I promise. I just - they have a good chem program too."

"Not as good as here. Bare, SCU is a perfectly fine safety school, but CCU's science program is nationally recognized. I love it, and I think you will too."

"I know all that," he said. "I still don't think I'm gonna apply."

"You'll get in. Your grades are - "

"I'm not afraid of not getting in," he said. "I just don't want to go. I don't want to be that far from Iris."

"You're making a decision that could affect the rest of your life, for a girl?"

"For _Iris,_ " he said, and hung up.

She called him back, and when he didn't pick up, ranted into his voicemail that he was being stupid and impulsive and short-sighted. He didn't call back, and he didn't text her back, either.

She made herself wait a day and calm down. "Listen," she said into her phone as she walked between classes. "I love Iris. I really do. Not just because you love her. I know I was kind of a wreck after Ronnie and I split. But I don't want you to think long-distance is impossible. It's not. You and Iris are perfect for each other and - " She swallowed. She'd thought she and Ronnie were perfect for each other too. "It can be done. It's not easy, but you can do it."

He called her back during class, on purpose. He knew perfectly well when her classes were, and that she turned off her phone. "It's not just Iris," he said. "In-state tuition's cheaper, and I can live at home. I don't want loans. I don't want to start out my life like that."

She called him back. "Everyone has loans," she said fiercely. "Welcome to the adult world!"

"Great!" he yelled. "So to be a grown-up, I have to be in debt for like thirty years?"

"I'm just saying that's not a reason to settle!"

"I'm not settling! You know what, you can talk all you want about CCU's nationally recognized department but you know what program they don't have that SCU does? Forensic science. It's four years and I'm qualified to work for any law enforcement agency - "

"Oh my god! You wanna be a CSI? They make nothing. It's a fucking city job. They wade in blood and piss and hair day after day. And it's not like TV, nobody knows their name!"

"I'm not you!" he yelled at her. "I don't need the blue ribbon every time. I don't need to change the world, I just want to help a little. I don't need everyone to know my name. That's you!"

She was the one who hung up that time.

She called Barry two nights later, while her roommate was out. "I - I talked to Cisco today," she said in a subdued voice. "We were going to figure out a way to get you to CCU and - and the more we talked - " Tears sprang to her eyes. "The - the more we talked, the more I figured out that - " The tears were rolling down her cheeks now, dripping off her chin. "That we wanted you to come to CCU for us. Not for you. Cisco wants his best friend to be his roommate, and I - I want my little brother around again. That's not - that's not a good enough reason to make you do something you don't want to do."

She took a shaky breath. "This is your decision. You don't need me to support it. I still think you could be something bigger than a CSI, and I still think you and Iris could make it long-distance, but that's not my call. And I'm going to stop fighting with you about it. And I - I'm going to try to support it. Even though I still don't agree."

Her phone rang in the morning, the ringtone in her ear jolting her out of a sound sleep. She sat bolt upright and grabbed it. "Barry?"

"I do care what you think," he said. "And I did like that I'd get to see you every day again. I miss you. But this is what I want. SCU, and forensic science, and Iris."

"I know," she whispered.

"I'm really sorry," he said in a trembling voice.

"Don't apologize. This is your decision. It's your life."

"I hate that things have to change."

"I know." She sniffed and wiped her eyes. "At least one thing won't change."

"What?"

"You're still a freaky mutant boy."

He laughed. It was shaky and watery, but it was a laugh.

* * *

It was easy to spot her brother in the crowd of graduates. One of the benefits of him being so tall. Caitlin hung over the railing, grinning as he picked Iris up and kissed her deeply, then set her down and looked up, searching until he spotted Caitlin. She waved, and he held his diploma up like he'd just gotten an Oscar. She laughed and gave him a "get up here," gesture. He kissed Iris again and said something, then started working his way through the crowd.

On the way, he high-fived a good-looking, vaguely familiar boy with shoulder-length hair. She squinted at him.

Barry came bounding up the steps and grabbed her in a hug so tight that her ribs creaked. She laughed up at him. "Oh my god, they actually gave it to you!"

"Right? I know! Where's Mom and Dad?"

"Waiting for the crowd to thin out a little. Who was that boy, by the way?"

"What boy?"

"The one you high-fived."

He looked at her like she was crazy. "Are you kidding?"

"No, who was he?"

"Caitlin, you didn't recognize Cisco?"

"Cisco? No way."

"Yeah, I told you he hit a growth spurt."

"You didn't tell me he changed that much."

Barry started to say something, and his expression changed. "Hoooo," he said. "Hoooooooooo! You think he's _hot_!"

"What! I do not!"

He fanned himself and put on a Southern belle accent. "Whah, Barry, Ah do declayah, who is that faaaaahn-lookin' _gentleman_ who hah-fahved yew?"

She poked him in the ribs. "Okay, a) that's absolutely terrible and b) I did not sound like that because c) I didn't recognize him and d) I thought I knew all your friends. That's all."

"And you were wondering when I got a _hot_ one!"

"Shut up!"

"I'm texting him right now," he said, yanking his phone out of his pocket. "Guess who thinks you're sssssa-mokin'!"

"Don't you dare. Don't you dare!"

"Ow, ow, I'm putting it away, ow, ear, ow - "

She let go and he rubbed his earlobe, grinning at her. She scowled back. He laughed and put his arm around her shoulders. She leaned into him. "Hey," she said softly.

"Um?" He was looking around again, trying to find their parents in the crowd.

"I'm proud of you, mutant."

He rested his chin on the top of her head. "Thanks."

FINIS


End file.
